Silencing the exhaust of internal combustion engines



L. G. HECTOR SILENCING THE EXHAUST OF INTERNAL COMBUSTION ENGINES Filed April 19, 1937 3 Sheets-Sheet l z/v VEN ram M iw/ za/n g7 fizz/2, %Mr m.

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SILENCING THE EXHAUST OF INTERNAL COMBUSTION ENGINES Filed April 19, 1937 3 Sheets-Sheet 2 IN l/EN 70A.

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L. G. HECTOR SILENCING THE EXHAUST OF INTERNAL COMBUSTION ENGINES Filed April 19, 1937 Patented Dec. 5, 1939 UNITED STATES SILENCING THE EXHAUST OF INTERNAL COMBUSTION ENGINES Luther Grant Hector, Buffalo, N. Y., assignor to Buffalo Pressed Steel Company, Buffalo, N. Y.

Application April 19, 1937, Serial No. 137,686

13 Claims.

leads to a closed chamber and the other of which.

continues through the mufiler, so that pressure pulsations passing'into the closed part of the passage are returned to the other part out of .phase with those pulsations which passed directly through the other part of the passage.

A further object of this invention is to provide a process and a muffler for converting the pulsating flow of gases entering the muffler into a relatively. steady flow when leaving the muffler,

by causing a part of the pulsations to pass directly through an outlet within the mufller and another part to be momentarily detained and then continued in their passage through the mufller out of phase with the pulsations of the part of the gases passing directly through the muflier. It is also an object of this invention to provide a process and a mufller in which the pressure pulsations entering the same are first doubled and then passed through a high frequency acoustic train or filter.

Another object of this invention is to provide a mufller of the return flow type with a conduit for gases having the inlet portion thereto with- 311 in the mufller formed so as to facilitate the entrance of gases and sound waves into the same, and at the same time effecting an equalization of flow in' the conduit.

It is also an object of this invention to utilize the momentum of gas in the pulsations to effect a .doubling of the pulsations and thus to produce a more uniform flow.

A further object of the invention is to provide a muffler having an outer shell of elongated cross section with improved means for reinforcing the outer shell.

Further objects of the invention will appear from the following description and claims. 50 In the accompanying drawings:

Fig. 1 is a longitudinal central sectional view of a muffler embodying this invention.

Figs. 2 and 3 are transverse sections thereof respectively, on lines 2-2 and 33, Fig. l. 55 Fig. 4 is a longitudinal sectional view of a mufller of modified construction, the section being taken approximately on line 4-4, Fig. 5.

Fig. 5 is a transverse section thereof on line 5-5, Fig. 4.

Fig. 6 is a transverse section of a muflier of 5 slightly modified construction taken on line 6-6,

Fig. 7.

Fig. 7 is a central longitudinal sectional view of the mufller shown in Fig. 6.

Fig. 8 is a fragmentary longitudinal sectional 10 view of a mufller similar to that shown in Fig. 7, but showing a slight modification thereof.

Fig. 9 is a fragmentary transverse sectional view on line 9 9, Fig. 8.

According to my proeess of silencing the noise 16 of an exhaust of an internal combustion engine,

I pass the exhaust gases into a muffler conduit having an outlet or discharge opening in the side thereof. At this outlet the gases during a pressure pulsation following the opening of an m exhaust valve of the engine are divided so that a portion thereof passes directly out of the opening and another portion thereof is carried by its momentum beyond the opening, into a suitable chamber which is substantially closed. Some of 25 the gases entering the chamber are returned to the outlet in the conduit after the peak of the pressure pulsation has passed through the outlet, thus resulting in a second rush of gases through the outlet. In this manner, two peaks or 3o pressure waves are produced from a single peak or wave initially discharged into the mufiier, and each wave will accordingly be of decreased intensity and the two waves will be out of phase with each other, thus producing a more uniform 5 and sustained flow of gases through the outlet.

I have illustrated my invention in the accompanying drawings as embodied in several different mufiiers, but it will be understood that this invention may be incorporated in many different constructions and it is not intended to limit this invention to the particular constructions shown.

Referring to Figs. 1 to 3, the muffler shown has an outer housing or casing comprising an outer shell I5 and two end heads l6 and I1, the shell in this particular construction being of elongated or substantially elliptical or oval cross sectional shape. The head I6 is provided with a flanged inlet opening i8 within which an inlet duct I9 is secured. The usual exhaust pipe leading from an internal combustion engine may be connected in any suitable or usual manner with the inlet duct 19. The other head I1 is provided with'a flanged opening 20 to which a discharge duct 2| 5 is secured which may be connected in any suitable manner to the usual tail pipe leading from the mufiler.

The gases entering into the mufiler through the inlet duct l9 are conducted to a conduit or shell 24, one end of which is connected to a part of the inlet duct l9, and this conduit 24 is provided with an outlet or discharge opening for gases, which may be in the form of a series of apertures 25 through which most of the gases received by the mufiler pass. These apertures, consequently, must be of sufiicient number and size so that their total area is sufiicient to permit all or most of the gases to discharge through these apertures out of the conduit or shell 24 without producing excessive back pressure in the conduit 24. In the particular construction illustrated, the gases after passing through the apertures 25 pass into a relatively large space 25 confined by the outer shell l5 of the muffler and then pass into a discharge conduit or shell 27! which connects with the discharge duct 26.

In accordance with this invention, a substantial part of the equalizing of the flow of gases through the mufiler is effected by providing in the mufiler a blind or substantially closed passage or chamber into which a portion of the gases enter during the peaks of the pressure pulsations and from which they are returned to the same path which that portion of the gases which passes through the muffler without entering the closed chamber or passage has followed. The time interval required for a portion of the pressure pulsations to enter into the blind or closed passage and then return to the main passage is sufiicient to cause these pressure pulsations to return into the main path of gases through the mufller out of phase With that portion of the pressure pulsations which has not passed into the blind or closed passage. In the particular embodiment of this'invention disclosed in Fig. 1, the main passage for the gases from the conduit 24 is through the apertures 25 thereof. The closed or blind passage for the gases is formed by a chamber 28 which, in the construction shown, is formed by means of an intermediate shell 29 having a bafile or annular supporting member 30 which forms a connection between the conduit 24 and the intermediate shell 29. The outer end of the shell 29 is closed by means of a bafie or head 3!. Preferably the intermediate shell 29 extends forwardly beyond the annular supporting baflie 30 about the opening or apertures 25 of the conduit 24, as shown at 32, so that the gases discharged through the apertures 25 will impinge against the portion 32 of the intermediate shell rather than directly against the outer shell which would under some conditions produce objectionable noise.

By means of the construction described, it will be seen that when a pressure pulsation enters into the conduit 24 resulting from the opening of an exhaust valve of the engine, the pressure wave or pulse, in passing the openings 25 of the conduit 24, will cause a portion of the gases to flow outwardly through these openings, while another portion will continue to flow straight through the conduit 24 and into the blind or substantially closed chamber 28. As the pressure within the conduit 24 decreases due to the discharge of gases through the apertures 25 and into the chamber 28, gases from the chamber 28 will return into the conduit 24 and pass outwardly through the apertures 25 therein, and these gases will form a second pressure pulsation or wave which will be out of phase with the pressure Wave or pulsation which originally entered the muffler. Consequently, the relatively large chamber 26 about the conduit 24 and within the outer shell l5 will receive twice as many pressure pulsations as originally entered the mufiler, and since the pressure pulsations are out of phase with each other, it will follow that the peak of one pressure wave will partly fill the trough of another wave. Consequently, the intensity of pressure variations will be very greatly reduced, and this in turn will result in a more uniform flow of gases out of the discharge conduit 22 of the mufiier, particularly since the relatively large chamber or space 26 will tend to further equalize these pressure pulsations. It also follows that instead of forcing all or most of the gases which enter the conduit 24 from the exhaust of a cylinder to flow through the openings 25 during a single pressure peak or pulsation, the flow of gases is divided into two portions, each of which flows through the openings 25 at reduced pressure and velocity and at different time intervals. This reduces the resistance to flow through the openings 25 as well as through subsequent flow passages in the muliler and through the tail pipe.

The pulse doubling chamber 28 also has a silencing effect upon the sound waves, since portions of some of the sound waves entering the mufiler will be discharged directly through the apertures 25, while other portions pass into the chamber 28 and are deflected back from the end wall 3! thereof and are thus caused to pass through the apertures 25 and in general, they will be out of phase with those portions of the sound waves which pass directly through the apertures 25.

The chamber 28 is preferablysubstantially imperforate so that the greater portion of the gas and sound waves entering the chamber from the conduit 24 will again pass out of the chamber into conduit 24. It may, however, be desirable under certain circumstances to provide in the intermediate shell 29 a few apertures 34 through which gases and sound waves may escape into the outer chamber 26 without passing back into the conduit 24 and through the apertures 25. These apertures 34- reduce natural resonance phenomena in the chamber 28 which might otherwise augment sounds of some frequencies. In addition, the apertures 34 have a further function in that any gases discharged into the chamber 26 through the apertures 34 will in general be out of phase with those portions of pressure pulsations which pass initially through the apertures 25 and with those which pass out of the apertures 25 after discharge from the pulse doubling chamber 28, thus further equalizing the flow of gases through the muilier. The total cross sectional area of the apertures 34 in the chamber 28 is, however, preferably less than the total cross sectional area of .the apertures 25 so that effective pulse doubling will result. The apertures 25, as shown in the drawings, are in the form of louvered slots, see particularly Fig. 2, although haust noises is produced, if the muflier is, provided with a high frequency acoustic train or series of high frequency resonator chambers into which the gases enter after they have been subjected to the pulse doubling action. In the particular construction shown for this purpose, I

have provided the discharge conduit 21 of the muffler with a series of groups of apertures 35 which may be spaced apart, and I have also provided about these apertures another intermediate shell 36 which together with transverse partitions or baffles 31, 38 and 39 forms high frequency resonator chambers 40 and 4|. The operation of these high frequency chambers is well known and the action of the same may be considerably augmented by providing in the conduit 21 a restriction arranged between adjacent groups of apertures so as to cause gases and sound waves to bypass the restricted portion of the conduit. I have, for example, shown in Figs. 1 and 2 an annular sleeve 42 which forms a restriction or contraction within the conduit 21 and which is spaced between two groups of-apertures 35, so that gases are caused to pass through theapertures 35 ahead of the restriction into the high frequency resonator chamber 40 and then back into the conduit 21 through apertures 35 located behind the restriction 42.

By a combination of the pulse doubling action and the high frequency acoustic train associated with the discharge conduit 2'1 an exceptionally effective silencing of exhaust noise is accomplished. This is probably due to an increased effectiveness of an acoustic filter in removing sound waves superimposed on a steady gas flow rather than sound waves superimposed on a pulsating gas flow. The silencing action of my improved muffler is particularly effective when the sound waves after the pulse doubling action, are passed into the large chamber 26 in which a cancellingof low frequency sound waves takes place.

I have also provided means for facilitating the entrance of gases and sound waves into the open end of the discharge conduit 21 from the large chamber 26. It will be noted in Fig. 1 that this conduit extends beyond the bafiie or transverse partition 3'! and this extension 43 of the inner conduit 21 is provided with apertures 44. This arrangement not only facilitates the entrance of gases and sound waves into the discharge conduit since the apertures 44 augment the cross section of the open end of this discharge conduit and produce in effect an entrance into the conduit comparable to a flaring or funnel-shaped entrance. Furthermore, those pressure pulsations and sound waves which enter through the perforations 44 will pass into this conduit ahead of mufflers of the return flow type and this is probably due to the fact that the flow of gas through the discharge conduit of the muffler and through the tail pipe is equalized to such an extent as to be relatively uniform so that the high resistance to flow offered by the tail pipe to the momentary high pressure and high velocity pulsations of gasesis avoided.

The muffler shown in Figs. 1 to 3 lends itself well to use in connection with an outer shell of elongated cross section, such as may be desired in places where the space available for the muffler is limited As is well known, outer shellsof other than circular cross section are subject to distortion due to internal pressures in the muffler, which may, for example, result from explosions of unburnt gases in the mufiier. It is, conse-'- quently, necessary to adequately reinforce outer shells of mufflers which are of non-circular cross sectional shape. In the construction shown, I provide an effective reinforcement for the outer shell of the muffler by'means of the intermediate shells 29 and 36 which are welded at intervals to each other, as shown at 47, and to the outer shell,

as shown at 48. It will be seen that when welded in this manner, a truss-like structure results which braces the outer shell I5. The provision of the transverse baffles or partitions in the intermediate shells 29 and 30 resist deformation of these shells due to strains thereon when the outer shell is subjected to pressure.

In Figs. 4 and 5, I have shown a muffler of slightly modified construction having an outer shell of approximately circular cross section. The inlet conduit 5| shown in this muflier cooperates with a pulse doubling chamber 52 in a similar manner as does the muffler shown in Figs. 1 to 3. In this muffler, the intermediate shell surrounding the discharge conduit 53 is of the type including longitudinal sections or parts 54 and 55 which have outwardly extending flanges which may be secured together by means of seams 56 or the like. The intermediate shells may be welded to each other, as shown at 57, and to the outer shell as indicated at 58.

In this modified form of mufiier, it will be noted that the two intermediate shells are arranged closer to one side of the outer shell than toward the other, and this arrangement is desirable when this muflier is to be used in place of mufflers of the kind heretofore commonly made, in which a return tube or shell is provided in which the gases flow from the back -to the front of the muffler before entering the discharge pipe or conduit 53. By means of the arrangement shown in Fig. 5, the inlet and discharge pipes of the muffler will be in the same relation to the outer shell as in mufflers having a return fiow duct. This arrangement provides for a large intermediate chamber 59 between the outer shell 50 and the intermediate shells within the muffler.

In operation, it will be obvious that the muffler shown in Figs. 4 and 5 is similar to that described in connection with Figs. 1 to 3.

In Figs. 6 and 7 is shown another mufiier having an outer shell 60 of substantially circular cross section and in which the centers of the inlet duct El and discharge duct 62 lie on a diameter of the outer shell 60. In this muffler, an inlet conduit 63 is provided which cooperates with a pulse doubling chamber 64 as in the constructions heretofore described and a discharge conduit 65 is provided with an acoustic train forming high frequency resonator chambers 66 and 6'! similar to those employed in Figs. 1 to 3 and having a restriction 68 which causes sound waves and gases to bypass into the high frequency chamber 65. In this case, the two intermediate shells of the muffler may be welded to each other and to the outer shell, as has already been described in connection with the other mufflers shown.

In Figs. 8 and 9 is shown a slight modification of the pulse doubling chamber. In these figures, "iii represents the outer shell and 'lll the inlet conduit having discharge openings "l2 from which the gases are discharged into the interior of the large chamber enclosed by the outer shell. i3 represents the intermediate shell having a baffle or head i l in the end thereof which with the annular baffle 75 forms a substantially closed pulse doubling chamber iii. In the particular construction shown in Figs. 8 and 9, the inlet conduit '1??? has a portion H which extends into the pulse doubling chamber iii and which is preferably provided with apertures 78 through which gases and sound waves may pass into the pulse doubling chamber. This construction is found to be desirable, in that it lets the gas expand more uniformly from the conduit into the chamber. This reduces the turbulence that results from gas breaking directly out of the relatively small conduit ll into the relatively large pulse doubling chamber. This construction also modifies slightly the doubling back of pressure pulsations, probably. because of slightly increased resistance to the flow of gases into and out of the pulse doubling chamber lb. The pressure pulsations passing out of this pulse doubling chamber and through the apertures F2 are slightly prolonged or delayed and thus under certain conditions serve to more fully equalize the flow of gases through the muffler.

In the construction shown in Figs. 8 and 9, there is also provided a discharge conduit m which forms with an intermediate shell M of the type shown in Figs. 4 and 5, high frequency resonator chambers 82 and 83 which form a part of a high frequency acoustic train.

It will be obvious that the operation and advantages of the various modified forms shown in the drawings are similar to those described in connection with Figs. 1 to 3.

I claim as my invention:

1. A mufller having an open ended continuous conduit which receives gases at one end thereof and which has a discharge opening therein spaced from the other end thereof, and a substantially closed chamber in which said other end of said conduit terminates, the wall of said chamber having perforations to reduce natural resonance of said chamber, whereby most of the gases discharged into said chamber are returned to said conduit and discharged through said opening therein.

2. A muliler having a housing including a outer shell and end headers having openings for the inlet and discharge of gases, a conduit Within said mufiler receiving gases from the inlet opening of one of said headers and provided with a gas discharge opening in a side thereof, an intermediate shell within said outer shell and having an open ended portion extending about said gas discharge opening of said conduit, transverse partitions forming with another portion of said intermediate shell beyond said opening a substantially closed chamber within which said conduit terminates, whereby gases discharged through said opening impinge against the portion of said intermediate shell extending about I said opening and whereby gas pressure impulses passingv into said chamber are returned to said conduit and pass out of said opening.

3. A mufller having a conduit which receives gases at one end thereof and which has a dis- .charge opening therein spaced from the other end thereof, and a substantially closed chamber into which the other end of said conduit extends, the portion of said conduit extending into said chamber having an open end and having apertures in the wall thereof, whereby the flow of gas pulsations discharged into said chamber is reversed, to return gases into said conduit for discharge through said opening therein.

4. A muffler having a housing, a conduit arranged therein to receive gases in one end thereof and having an outlet in a side thereof, a substantially closed chamber formed in said muflier and in which the other end of said conduit terminates, said chamber receiving those portions of gas pressure impulses which have passed said outlet without discharging through the same, said portions being reversed in said chamber and then returned to. said. outlet, a discharge conduit arranged in said housing for receiving gases therefrom and having perforate portions spaced from the gas receiving portion of said discharge conduit, and a shell arranged about said perforate portions to form therewith a high frequency resonator chamber,

5. A muffler including an outer housing enclosing a space within said muffler, a conduit in said mufiler and receiving gas pulsations and having an outlet past which said pulsations may travel and through which a portion of each pulsation may pass into said space, a substantially closed chamberformed in said space and communicat- "ing with an open end of said conduit for receiving another portion of each pressure pulsation and returning the same to said conduit for discharge through said outlet, a discharge conduit extending into said space for receiving gases from said space in the open end thereof and having perforate portions, and a shell surrounding perforate portions of said outlet conduit to form therewith high frequency resonance chambers.

6. A mufiler in accordance with claim 5 charac-- terized in that said chamber is provided with a series of apertures having a combined area less than the cross sectional area of said conduit and through which portions of gas pressure impulses entering said chamber may pass into said space.

'7. A mufiier including a housing enclosing a space, means for discharging gases and sound waves into said space, a discharge conduit extending into said space and having an open end terminating therein and provided near said open end with perforations, whereby gases and sound waves from said space may enter saidconduit through said open end thereof and through said perforations, said conduit being provided with other perforations, an intermediate shell surl rounding said other perforations and forming with said conduit high frequency resonator chainbers.

8. A mufiler including a housing enclosing a space, means for discharging gases and sound waves into said space, a discharge conduit extending into said space and'having an open end terminating therein, said conduit having perforations, an intermediate shell surrounding said perforations and forming with said conduit a high frequency resonator chamber, a portion of said conduit adjacent to the open end thereof extending beyond said high frequency resonator chambers and being provided in the wall thereof with perforations whereby gases and sound waves from said space may enter said conduit simultaneously through the open end thereof and through said perforations.

9. A muffler including an outer shell of elongated cross sectional shape, a pair of intermedicontacting portions and having opposite sides thereof welded to said outer shell, whereby the intermediate shells form a brace for the outer shell to retain the same in its elongated cross sectional shape,

10. A muiller including an outer shell of elongated cross sectional shape, a pair of intermediate shells arranged within said outer shell, said intermediate shells having portions of their peripheries in contact with each other and welded together at their contacting portions and having opposite sides thereof welded to said outer shell, whereby the intermediate shells form a brace for the outer shell to retain the same in its elongated cross sectional shape, and transverse bailies arranged within said intermediate shells and serving to maintain the intermediate shells in their original cross sectional shape when subjected to strains.

11. A mufller having a substantially continuous conduit provided with an outlet in a side thereof and having an open end, said outlet being proportioned to permit approximately half of a gas pulsation passing through said conduit to pass through said outlet, the remainder of said pulsation being discharged through said open end, a substantially closed chamber in which said open end terminates, said remainder oi said gas pulsation entering said chamber and returning to said conduit and then being discharged through said outlet, an outer shell enclosing said conduit and chamber and forming an enlarged space into which gases are discharged from said opening, means for conducting gases from said large chamber out of said mufller, and a high frequency resonator chamber associated with said means.

12. A muifler having a housing including an outer shell and end headers having openings for the inlet and discharge of gases, a conduit with in .said mufller receiving gases from the inlet opening of one of said headers and provided with a gas discharge outlet in a side thereof, an intermediate shell within said outer shell and forming a closed chamber about the discharge end of said conduit, whereby a portion of each pressure pulsation entering said conduit is discharged through said outlet and a second portion is discharged into said chamber and is reversed and returned in part to said outlet in said conduit, said intermediate shell being provided with aper-' tures communicating with, the space confined by said outer shell, the combined area of said apertures being less than the area of said outlet in said conduit.

13. A mumer having a housing including an outer shell and end-headers having openings for the inlet and discharge of gases, a conduit within said muii'ler receiving gases from the inlet opening of one of said headers and provided with a gas discharge outlet in a side thereof, an intermediate shell within said outer shell, and into which said conduit extends and which forms a substantially closed chamber about the discharge end 01' said conduit, the portion of the conduit extending into said chamber being perforate.

LUTHER GRANT HECTOR. 

